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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cf620d4c303df77f11529403f95929e9e9b170798b1494386190301f5e783ded' 
  AND token = '7K0yG944cfx4gGJXfp8Q9ZAI2aI52epe5nMdoLYUGb0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}