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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b638bcc31f107751090ad881b3d485c0dd40ec653fc2b91df62a852504dc4a78' 
  AND token = 'BITM9bLrzaR3ZjykegQTY1JW8clnieb02fu/5XncE+c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00013

JSON explain

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