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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '744dd14150099c9f84ff066c2621ce299f20dda30ce6fdb2d8229c1d7c8456eb' 
  AND token = 'mxu+Hk1w2ZC/tDqvH+l9RcgpQRe/3PlUdLqpDtsi+G4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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