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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '831a7785667fc2c3e48aa5f2311dd1b14bba3e457d5e80fa58fe2976ae335a2e' 
  AND token = '8/pUD3NNSz7eDuTP5o+DNx/PN/7dYbQ/ATZ7q2kN2Ek=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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