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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ec91e6a9b58cf2a5944d03288073dda3faa064d1ebb8b8924fd1bd2ff0b572e8' 
  AND token = 'b+mPEO5oUiz76/6KoRQPQQtqEcvXJbrq+ImdFJT3x94=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00009

JSON explain

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