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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c4dfe67720223067ca27f1412de42076ffe3eeffc19a2993f37d60fce62c590' 
  AND token = 'FjaBlurzavJwG2AinmedC93X+tUBEujGG5xHZy3n9aI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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