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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8c71db5bcee7dc7f498b24a3a6687af74086b46f06f6aba48f77ba7c9209caf' 
  AND token = 'PYcN4PL3XMfBpyhjCAmHXEqZUygcnAz+IkjTpdpeJ7M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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