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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c91ffe7587591cc21721c61576f1daac2f0ae12d3adec68043135c4c75621e2f' 
  AND token = 'UM+qWRlXL5ERWu596cwHpVCyCIqBUubBDay464I+LBs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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