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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b304c883114c40eaccfcffee1e402f12554fa0732a46b4c4ffe7df4332708c00' 
  AND token = 'K4pPLDAKi2DTNkJPRJ3LcEfIVD46b8f/tQOvLZjObF8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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