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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c7f3b18f321bd33dd4ce74e64778eccd247ab1ff32c9c834c0a37f9fba19d918' 
  AND token = 'jh6TB5i/P/T+mGHkB5Lr77smrSEnOY6oYM2QsEFw5xQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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