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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6c76e74d2fdc4ec44f86f28b5d41dc2853bdc3918e29dfa4d901e41ca83a20e' 
  AND token = 'lrr91YZ26LeShZMelzVS+R9KGf+O+Z1JakyaiERHIRY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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